1. Field of Invention
The field of the currently claimed embodiments of this invention relates to electronic and electro-optic devices, and more particularly to simplified electronic and electro-optic devices that utilize novel pn-semiconductor structures.
2. Discussion of Related Art
In conventional pn-junction devices, charge collection from the energy capture or photon sensing surface requires application of a transparent conducting electrode or patterned metal grid. Not only is this costly, but it also reduces device performance, e.g. by blocking some of the incident solar energy in a photovoltaic.
FIG. 1 is a schematic illustration of a conventional photovoltaic cell 100. Such conventional devices typically have a metal electrode 102 that may be part of, or formed on a substrate. The photovoltaic cell 100 has an n-type (or p-type) semiconductor layer 104 formed on the metal electrode 102 and a p-type (or n-type) semiconductor layer 106 formed on the n-type (or p-type) semiconductor layer 104 such that a pn-junction is formed therebetween. A “transparent” electrode 108 is formed on the p-type (or n-type) semiconductor layer 106. The metal electrode 102 is electrically connected to a first electrical lead 110 and the transparent electrode 108 is electrically connected to a second electrical lead 112.
A common material for the transparent electrode 108 is indium tin oxide (ITO) due to its good electrical conductivity and its relatively good transparency. However, even though ITO has relatively good transparency, there is still significant absorption of light. In addition, indium is not very abundant, so it is becoming very expensive and it is becoming more difficult to meet demand. There has thus been a lot of effort directed to developing new materials such as networks of nanowires and/or graphene to replace conventional transparent electrodes. However, to date, all such conventional electrodes have less than adequate transparency and/or conductivity, or are expensive due to base materials and/or manufacturing requirements. Therefore, there remains a need for improved electro-optic and electronic devices.